Colour photography



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2,923,627 I COLOUR PHOTOGRAPHY Leslie Frederick Alfred Mason, Ilford,England, assignor to Ilford Limited, Ilford, England, a British companyNo Drawing. Application March 31, 1958 Serial No. 724,931

This invention relates to colour photography and more particularly todeveloping compositions for use in colour photographic processes. I

In one well-known method of colour photography a colour image is formedby developing a silver salt image in a photographic element by means ofa developing solution which contains an aromatic primary aminodeveloping agent and a dye intermediate (hereinafter referred to as acolour coupler) such that the oxidation products of the developing agentformed during its developing action couple with the colour coupler toconstitute a dye in situ with the developed silver image, the dyecommonly being anazomethine or quinone-imine dye.

The developing agents used in this type of process are usuallyderivatives of p-phenylene diamine, well-known examples beingN.N-diethyl p-phenylene diamine and 2- nited States Patentamino-S-diethyl amino toluene and their salts and sulphur dioxidereaction products. These agents unfortunately have a tendency to oxidisein the air and, since the oxidation products will combine with thecolour coupler present, the solutions in use acquire, more or lessrapidly, a scum consisting mainly of the dye thus formed. This is soserious a difficulty that such developers must frequently be discardedlong before they have outlived their useful activity.

The extent of scum formation depends on the extent of aerial oxidationwhich occurs, and this in turn is found to be greatest at higher pHvalues. Accordingly, a balance must be struck between the activity ofthe developer, which is reduced by lowering the pH of the solution, andthe liability of the developer to oxidation, which is increased byincreasing the pH of the solution, i.e. some sacrifice of developeractivity must be made in order to aviod undue oxidation. Generally, thepH of the solutions is adjusted to about 10.5.

In an effort to overcome this difficulty, various antioxidants have beendescribed for inclusion in the de veloper, probably the best known beingascorbic acid. However, the inclusion of such'anti-oxidants generallycauses some loss in developer activity. Moreover, only very smallquantities must be used so that the addition of the precise quantityrequired in any particular case is a highly critical operation.Moreover, they generally only hold the solution against scum formationfor a matter of 2 to 3 hours.

It has been proposed to include hydroxylamine or a salt thereof incolour developers as an anti-oxidant or preservative. However, onattempting to use this additive for a colour developer containing colourcoupler, at the usual pH value of about 10.5, it was found that itfailed entirely of its purpose, i.e. it had little or no effect on theformation of dye scum.

It has been found, however, that if the pH of the developing solutioncontaining a colour coupler is increased, so that the tendency'toformdye scum is enhanced, the addition of hydroxylamine or a salt thereofbecomes cfwill be appreciated that this result is highly surprisingsince an increase in pH would have been expected to make the positionworse rather than better.

Thus, a photographic developing composition for use in colour developinga developable sliver salt image in a photographic element may comprisean aromatic primary amino developing agent, a colour coupler which iscapable of combining with the oxidation products of such developer toform a dye, and hydroxylamine or .a salt thereof, the said. compositionon dissolution in water having a pH of .at least 11.25.

Whilst developers thus formulated are of very considerable value it is,as noted above, based on the possibility of using developing solutionsat pH values of at least 11.25. In some developing steps, however, suchhigh pH values are not practicable since they lead to otherdifiiculties.

In British Patent No. 782,304 it is explained that resistance to aerialoxidation in developers of the character referred to above can also beobtained by the inclusion in the developer of a small quantity of a 4-aryl-2-oxytetronic acid or 4-aryl-2-oxytetronirnide. These compounds maybe written in tautomeric form as follows:

0 0 OH OH ll I -CH s v =-V-C R-CH 'J=x R-CH d=x 0 H V r r o where R isan aryl group or a substituted aryl group and X is an oxy'g'enatom'or'animino group. The aryl group -R may be a phenyl'or naphthyl groupor a corresponding group containing, for example, alkyl, aralkyl, aryl,sulphonic acid or halogen substituents. Specific compounds of value are:1'

4-phenyl-2-oxytetronimide 4-o-sulphophenyI-Z-oxytetronimide4-o-chlorophenyl-2-oxytetronimide 4-o-chlorophenyl-2-oxytetronic aciddelays scum formation for periods of the order of 12 hours, or evensubstantially longer.

According to the present invention therefore a photographic developingcomposition for use in colour developing a developable silver salt imagein a photographic element comprises an aqueous alkaline solution of anaromatic. primary amino developing agent, a colour coupler which iscapable of combining with the oxidation products of such developer toform a dye, hydroxylamine or, a 'salt thereof and ascorbic acid and/ ora tetronic compound of the formula above set forth. The inventionfurther includes processes of colour development employing suchsolutions.

It is to be understood that the specific description of the productionof the tetronic' compounds is to be found in British Patent No. 782,304.Y

The proportions of hydroxylamine and ascorbic acid or tetronic compoundare not unduly critical. Generally a quantity of the orderof 0.5 to 1.5g./litre of hydroxylfective in reducing, or even eliminating, dye scum.It

, agents. are N.N.-diethyl p-plienylene diamine or '2-a'mino- 5'-diethylamino .toluene, or:theirsalts. or sulphur dioxide Patented Feb. 2, 1960reaction products. A suitable alkalinity in the developing compositionis conveniently achieved by the use of alkali carbonates or, where ahigh pH is desired, mixtures of tribasic sodium phosphate and dibasicsodium phosphate, these latter compounds being particularly useful owingto their good buffering properties.

It will be appreciated that thedeveloping compositions of the inventionmay include other ingredients common to photographic developers, e.g.alkali, ammonium or amine sulphites and alkali or ammonium bromides. itis also frequently of advantage to include a proportion of ethyl alcoholin the developer.

Where the developing compositions are formulated and marketed ratherthan being used directly, it is generally desirable that the colourcoupler and the alkali should be packed separately from the developingagent, hydroxylamine and ascorbic acid or tetronic compound as referredto above. The invention accordingly further includes in solid form or instrong aqueous solution a composition of aromatic primary aminodeveloping agent, hydroxylamine and ascorbic acid and/or tetroniccompound as defined.

The following examples, inwhich the developers identified as developersD, E, F, G and H are in accordance with the invention, will serve toillustrate the invention:

photographic element which comprises anaqueous alkaline solution of anaromatic primary amino developing agent, a colour coupler which iscapable of combining with the oxidation products of such developer toform a dye, a. compound selected fromthe class consisting ofhydroxylamine and its salts in a concentration of 0.5 to 1.5 g./litreand a compound selected from the class consisting of ascorbic acid andtetronic compounds of the formula:

Examples Developer formulations A B O D E F (3- Sodium carbonate 10 I10) g 80 80 80 80 80 80 80 Sodium hexametap osphate g- 3 3 3 3 3 3 3Hydroxylamine hydrochloride -.g.. 1 l 1 1 1 Ascorbic acid a 0.2 0.2 -14-o-sulphophenyl-2-oxytetronimide- Q 0. 2 0. 24-o-chlorophenyl-2-oxytetrnnimid 2' 0.2 4-pheny1-2-oxytetrnnim g 0. 2Sodium sulphite .-g 5 5 5 5 5 5 5 Potassium bromide g 2 2 2 2 2 2 2Industrial spirit 74 0.1 ec 150 150 150 150 150 150 150l-Hydroxy-il-naphthoyl cyclohexylamide g 2 2 2 2 2 2 22-Amino-5-diethylamino toluene g- 2 2 2 2 2 2 Water to make cc- 1, 0001, 000 1, 000 1, 000 1, 000 1, 000 1, 000

Delay period in onset; of scum in hours (approx.) nil 2 2 12 12 12 48When, in Developer G the tetronimide was replaced by4-phenyl-2-oxytetronic acid (Example H), a similar delay in scumformation for 48 hours was obtained.

The pH of the developer was in all cases approximately 10.50. It will beseen that while hydroxylamine alone is ineifective at this pH, and bothascorbic acid and a typical tetronic compound afiord only limitedprotection against scum formation, the combination of the two(developers D, E, F, G and H) shows a very much enhanced protectiveeflect.

What I claim is:

1. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous alkaline solution of an aromatic primary amino developingagent, a colour coupler which is capable of combining with the oxidationproducts of such developer to form a dye, a compound selected from theclass consisting of hydroxylamine and its salts and a compound selectedfrom the class consisting of ascorbic acid and tetronic compounds of theformula:

where R is selected from the class consisting of phenyl and naphthylgroups, and phenyl and. naphthyl groups containing alkyl, aralkyl, aryl,sulphonic acid and halogen substituents, and X is selected from theclass consisting of the oxygen atom and the imino group.

2. A photographic developing composition for use in. colour developinga-developable. silver. salt image, irra developing agent, a colourcoupler which is capable of combining with the oxidation products ofsuch developing agent to form a dye, hydroxylamine in a concentration of0.5 to 1.5 g./litre, and ascorbic acid in a concentration of 0.1 to 0.5g./litre.

4. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing agent to form a dye,hydroxylamine in a concentration of 0.5 to 1.5 g./litre, and 4-phenyl-2oxytetronimide in a concentration of 0.1 to 0.5 g./litre.

5. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing agent to form a dye,hydroxylamine in a concentration of 0.5 to 1.5 g./litre, and4-phenyl-2-oxytetronic acid in a concentration of 0.1 to 0.5 g./ litre.

6. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing agent'to form a dye, alkalicarbonate, hydroxylamine in a concentration of 0.5 to 1.5 g./litre, andascorbicacid in a concentration of 0.1 to 0.5 g./ litre.

7. A photographicdeveloping. composition for use-in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing agent to form a dye, alkalicarbonate, hydroxylamine in a concentration of 0.5 to 1.5 g./litre, and4-phenyl-2- oxytetronimide in a concentration of 0.1 to 0.5 g./litre.

8. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing agent to form a dye, alkalicarbonate, hydroxylamine in a concentration of 0.5 to 1.5 g./1itre, and4-phenyl-2- oxytetronic acid in a concentration of 0.1 to 0.5 g./litre.

9. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element, which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing agent to form a dye, tribasicsodium phosphate, dibasic sodium phosphate, hydroxylamine in aconcentration of concentration of 0.1 to 0.5 g./litre.

11. A photographic developing composition for use in colour developing adevelopable silver salt image in a photographic element which comprisesan aqueous solution of pH 9 to 11.25 of an aromatic primary aminodeveloping agent, a colour coupler which is capable of combining withthe oxidation products of such developing 0.5 to 1.5 g./litre, andascorbic acid in a concentration of 0.1 to 0.5 g./litre.

10. A photographic developing composition for use in colour developing adevelopable silver salt image in a agent to form a dye, tribasic sodiumphosphate, dibasic sodium phosphate, hydroxylamine in a concentration of0.5 to 1.5 g./litre, and 4-pheny1-2-oxytetronic acid in a concentrationof 0.1 to 0.5 g./1itre.

References Cited in the file of this patent UNITED STATES-PATENTS2,286,662 Weyde et al. June 16, 1942 2,401,713 Vittum et a1 June 4, 19462,656,272 Gunther Oct. 20. 1953 FOREIGN PATENTS 751,304 Great BritainJune 27, 1956

1. A PHOTOGRAPHIC DEVELOPING COMPOSITION FOR USE IN COLOUR DEVELOPING ADEVELOPABLE SILVER SALT IMAGE IN A PHOTOGRAPHIC ELEMENT WHICH COMPRISESAN AQUEOUS ALKALINE SOLUTION OF AN AROMATIC PRIMARY AMINO DEVELOPINGAGENT, A COLOUR COUPLER WHICH IS CAPABLE OF COMBINING WITH THE OXIDATIONPRODUCTS OF SUCH DEVELOPER TO FORM A DYE, A COMPOUND SELECTED FROM THECLASS CONSISTING OF HYDROXYLAMINE AND ITS SALTS AND A COMPOUND SELECTEDFROM THE CLASS CONSISTING OF ASCORBIC ACID AND TETRONIC COMPOUNDS OF THEFORMULA: